Test probe



Patented Mar. 23, v1948 UNITED STAT ES:- PATENT GFFICE 'res-T moet William G. Eckhard, Stanhope, J. Application August z2, 1945, serial No. 611,933

This invention' relates to electrical Vcontact members and more speci-callv to test probes- Whl'ch are used in connection with apparatus 'for making electrical tests or measurements con fined spaces.

It is an objectvoi this invention to provide .an improved test probe which is simple to `construct and which is! particularly adapted for use in mai;- ingcontact with electrical Wires or terminal-members which arecloselyadjacent to other wiresfo-r terminal members. Y

In theart of testing radio-and other-electronic equipment, there has long been a need for a test probe which can vquickly and easily, and Withouty causing shorteclrcuits, make contact with a Wire or terminal member inthe `interior of av mazey of Wires and' othery electrical conducting mesnbers such as is commonly found in the chassis of a radio set. Moreover, the advent of the miniature vacuum tube vhas made the electronic equipmentV utilizing such tubes, even more` compact. and the need for a suitable probe for testing'themand for making contact with their sockets even vmore pressing; While various probes have beerrsubgested and made for this purpose, none ofthem has the ovenalladvantageszfonnd in the. improved probe. of this invention.

'It is another object of .this invention 'to provide an improvedA probe which oers a minimum of' contact surface While being moved to 'a contact point but which can be easily manipulated by the lingers of one hand to increase the contact surface.

It is still another object of .this invention vto provide a probe and which probe has improved holding properties when compared with other easily detachable probes.

.Other objects of the invention as Well. vas various features thereof will be apparent from the description which follows,

In accordance with the invention, thereis pmvided, by way of example for illustrative purposes, a novel test probe which has many advantages over those of the prior art. This probeis: provided with a long metallic contact member terminatng in a head portion which has a pointed member and a hook. The pointed member vis adapted to 'make ready contact with miniature tube sockets and it may have a chiselededge, if desired, to reduce slippage on round Wires. The hook makes it possible to hook onto a desired portion of an electrical circuit, such as a wire or terminal. The interior surface of this hook is which has a novel .contact head' portion for making an excellent electrical contact 2y Claims. (Cl. 173-42713) preferably formed into a blunt. -\/v ,orv knife edge to improve `the contact'. The contactv member is completely yprotected texcept'for the head) by inea-ns :of an insulating sheath which can be moved, by means `of a. simple finger motion, in a direction away from the. head, thus exposmg more .of the head end of the. contact member. This construction makes yiti possible to keep the exposed contact surface at a minimum. while passing theprobe through a maze of wires'and Contact. elements .and to enlarge the contactJ area when desired. vThe end surface oi the '1nsulating sheath near the Vend .can be roughened or serrated to improve the Vholding properties of the probe.

The. invention will be more .readilyunderstood bg.' referring to the following descriptionitaken'in connection with the accompanying drawings formingv a part thereof, which:

Fig'. Y1 isa side vievv'oi a probe in accordance with the invention;

Fig. 2 is a cross-'sectional view of the probe of Fig. 1';l

Eig. It a side View of the. probe of Ylitre. l show ing. the inner `casing member in ythe retracted position;

Figs, @and 5. are iperspectivefvieWs-oi thehead portions of vContact, memberswhich are modifications ot those shown in Figs. 1, 2 andI 3; and

Fig. 6 is kefrrenlarged Across-sectional' View taken in la Inlane through the line 6--61 in Fig'. 3.

Referring more specificallyto the drawings, Figs. l, 2 and -3 show, by' way of exanmle for illustrativexpnrposesand iny side'view, aprobe or prod Il) in accordemce'with this invention. The probe comprises an outer cylindrical casingmember ,Iii ci any high gradeinsnlatng material which has an opening atene end thereof to receive aninner casing member i12 which comprises a hollow tube i3 of .insulating material forced into, cemented or otherwise attached to. a hollowf'tube L4 which also-oi insulating: material. The tube M is of such diameter that vit makes ,a goed sliding nt inside the outerv casing li and is `provided. with acollar or .other `finger hold' member t5 upon which va goed viingerfgrincan beobtainedto move the member :i4- back within thefonter casingA mene bert l, against thepressure ofra springv Imounted between Washers I1 and i8 therein. Inthe fullyretracted position, the collar-I5'- assumes the Vposition shown in Fig. 3.

The end of the casing member Il remote from the collar 'I5 is closed by a cap I9 which has an opening therein through which a. terminal wire 20 can pass. The wire 20, which is adapted to have its outer end connected to any suitable device such as an oscilloscope, is connected, by soldering for example, to a hook 2| on the end of a metal contact member 22. This contact member extends through the entire length of the tube I3 and terminates in a head 23.V It will be readily appreciated that when the collar I5 is moved towards the outer casing member II, by taking the collar between two ngers of one hand and moving it towards the base ofthe probe, for example, the head 23 has more of its surface exposed, Yas shown in Fig. 3, of Figs. 1 and 2.

The head 23 of the contact member 22 is provided with a short hook 24 which is preferably pointed, as shown in the drawings, and may have about one half to two thirds of the inside of its neck formed into a blunt edge and the balance (preferably the part 21 substantially parallel to the end surface of the sheath I3) formed into a V or knife edge (see Fig.V 6) to improve the contact. A spur point 25 is added to improve the usefulness of the probe so that contact in miniature tube socket holes can easily be made. A short slender point is nection (see Fig. 4). If desired, the member 25 can have a chisel edge to reduce slippage on round wires. This is shown in Fig. 5. Figs. 4 and 5 also show the end 26 of the insulating tube I3 roughened or serrated to give a good grip on a wire or lug terminal when the hook 24 is used for making electrical connections thereto.

The cap I9 is provided with an inner portion 21 which is a threaded sleeve, preferably tapered and slotted so that it will compress the insulation of the lead or terminal wire 20 when the cap I9 is screwed in tightly.

The member I3 is preferably made long and slender so that access can be had to contact elements well within the interior of a maze of wires in a radio chassis, for example, without causing short circuits. Y kWhen the wire or member to which it is desired to make contact is found, the collar I5 can be moved back with two ngers of one hand (leaving the other iingers of the same hand and al1 of the other hand free for other purposes', such as manipulating other test probes, and reducing the danger of shock to the operator and damage to the equipment). This exposes more of the head 23 so that a wire can be partially encircled with the hook 24 and gripped tightly between this member and the serrated or roughened end 25 of the tubing I3 when the collar I 5 is released and the spring I6 allowed to force the tube I3 to its protracted position (Fig. l). The special shape of the inner edge of the hook improves the electrical contact since the V or knife edge 21 penetrates any films of oil, 'grease and the line. If the member to which it is desired to make contact is a miniature tube socket or a wire or otherelement that is impossible to encircle with the hook, the pointed or chiseled edge 25 is used. If the hook 24 is used with a Wire or the pointed or chiseled edge 25 used with a socket opening, the probe will make sustained contact even though the hands are removed. The probe in accordance with the invention makes it possible to make fast connections4 and disconnections safely.

Various changes can be made in the embodithan when it is in the position desirable for this type con' ments described above without departing from the spirit of the invention, the scope of which is indicated in the appended claims.

What is claimed is: 1. An electrical contact member adapted to y make contact with a wire or terminal member comprising a first insulating casing member which is open at one end thereof, a second insulating casing member adapted to make a sliding ,Y trical terminal and which extends through said opening in the end thereof and through said entirefsecond casing member to terminate in a, hook-shaped clip, and resilient means in the interior of said first casing member positioned to force said second casing member toward and sufciently close to the inside surface of the hook of said clip so that the wire or terminal `member can be tightly gripped between the end of'said second casing mem-ber and the inside surface of said hook. f

2. An electrical `contact member adapted to make contact with a wire or terminal member comprising a rst insulating casing member which is open at one end thereof, a second insulating casing memberadapted to make a slidingy fit with said first casing member so as tomove freely with respect thereto in a lateral direction andA having an end surface outside said first member, a metal contact member which has one end fastened within said rst casing meme berto an electrical terminal and which extends through said opening in the end thereof and through said entire second Vcasing member to terminate in a hook-shaped clip, and resilient means in the interior of said rst casing member positioned to force said second casing member toward and suii'iciently close'to the inside-surface of the hook of said clip so that the wire or terminal member can be tightly gripped between the end of said second casing member and the inside surface of said hook, a portion of the inner surface of the hook which is substantially parallel to the said end surface of the secondk casing member having a knife edge and portions of vsaid clip inner surface on each side of said knife edge being blunt.

\ WILLIAM C. REICHARD.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Y Date 846,158 Stewart Mar. 5, 1907 1,027,090 WaXbon V May 21,1912 1,378,801 Lamb May 17, 1921 1,650,779 Williams NOV. 29, 1927 1,833,835 Hieronymus Nov. 24, 1931 2,105,833 Feuer Jan. 18, 1938 2,222,110 Maurer Nov. 19, 1940 2,292,236 Martin I Aug, 4, 1942 FOREIGN PATENTS l Number Country Date Italy Mey 3, 1932 

